why does CCl4 have a higher boiling point than BrF?

Both CCl₄ and BrF are both molecular, and the molecules are held together by van der Waals' forces. The molecular size of CCl₄ is greater than that of BrF, and leading to greater van der Waals' forces between CCl₄ molecules. Therefore, CCl₄ has a higher boiling point than BrF.

BrF exhibit minor dipole Forces which are slightly stronger than London dispersion forces, which exist in CCl4, meaning that BrF should have a higher boiling point that CCl4. However, because CCl4 is such a large molecule compared to BrF, it has a much larger more polarizable electron cloud. In other words, the electron cloud in CCl4 is much larger and therefore has a strong dispersion forces between each CCl4 molecule.